Computer Science

• The order of the storage units are.. Nibble, Bit, Byte, Kilobyte, Megabyte, Gigabyte, Terabyte
• The definition of resolution is the total number of pixels in an image
• up to 2 colours = 1 bit

  up to 4 colours = 2 bits

  up to 8 colours = 3 bits

  up to 16 colours = 4 bits

  up to 32 colours = 5 bits
• Lossless compression will not loose any of the original data
• Lossy compression permanently looses some of the data
• ADC is an analogue to digital converter. It converts analogue signals into digital signals
• Binary addition 0+0 = 0 , 0+1=1 , 1+0=1 , 1+1= 0 carry 1 , 1+1+1 = 1 carry 1
• Sample rate is the number of samples recorded in any given period of time
• Sample rate is measured in Hz (Hertz)

  1Hz = 1 sample per second
• System software provides a platform for other software to work.

  It includes operating systems and utility programs
• Run length Encoding uses frequency / data pairs to encode each run length of the same coloured pixels
• The sound file size formula is: sample rate (Hz) * sample resolution (bits) * duration (s)
• Operating Systems manage computer hardware, users and the resources used on software

  Manages:

  • the processor
  • the memory
  • the input/output
  • the applications
  • the security
• Sample resolution is a measure of how much data is processed for each second of sound
• High-Level Language generally have statements that look a bit like english or maths

  (example: Python, Visual Basic, Scratch)
• Low-Level Language is assembly language or machine code

  (example= binary)
• An interpreter translates source code into machine code and immediately runs it
• A compiler translates high level language into machine code
• An Assembler translates assembly code into machine code so it can be run later
• The 2 main types of system software include: system software and application software
• Utility software includes:

  • encryption software
  • defragmentation software
  • data compression
  • disk clean-up tools
  • disk formatters
  • anti-virus software
• The main components of a CPU are;

  • control unit
  • ALU
  • registers
  • cache
• What are the CPU's two MAIN components?

  Control Unit and Arithmetic Logic Unit (ALU)
• What is the processor speed and how does it affect the performance of a computer?

  Processor Speed is how quickly a computer can process instructions

  The processor speed affects your computer because the more powerful and updated your processor is, the faster your computer can complete its tasks.
• What factors affect the performance of the CPU?

  • cores
  • cache size
  • clock speed
• How does the number of cores affect the performance of the CPU?

  CPU's with multiple cores have more power to run multiple programs at the same time
• How does the cache size affect the performance of the CPU?

  The larger the cache size, the more data it can store and the faster the system performance is , by reducing the need for the processor to access slower main memory.
• How does the clock speed affect the performance of the CPU?

  A higher clock speed means a faster CPU. This means that apps can run faster and smoother
• What are embedded systems?

  The CPU speed is typically slow.

  The software has one purpose, so it can't install new software

  Storage --> programs are stored on ROM

  Reliability --> they are typically very reliable

  Examples of embedded systems include; washing machines and dishwashers.
• What are non-embedded systems?

  The CPU speed is typically very fast.

  Software --> new software can be installed

  Storage --> programs are stored on hard-drives

  Reliability --> runs many softwares so it may be less reliable and may need restarting.

  Examples of non-embedded systems include: desktop computers, laptops, tablets, smartphones
• What is the purpose of the CPU?

  • processes instructions
  • carries out all the instructions for the computer
• What is a register?

  A fast memory location in the CPU
• What is the cache?

  • Located in the CPU
  • Slower to access than the register
  • stores instructions that were recently used / frequently used
  • It is closer to the CPU than the RAM, meaning that it can provide data and instructions at a higher rate.
• Different types of secondary storage methods include:

  • magnetic
  • optical
  • solid state
• What is magnetic storage?

  Mechanical parts move over the disks surface to read and write data magnetically, or a drive head reads a magnetic tape
• What is optical storage?

  Lasers read and write data using light
• What is solid state storage?

  Data is recorded onto solid memory chips without any moving parts
• What are the basic features of magnetic disks?

  They...

  • contain concentric circles called tracks
  • each track is divided into sectors
  • disk heads are mounted on mechanical arms read and write the data
• What are the advantages of Magnetic Disks?

  They....

  • cheap
  • large storage capacity
  • relatively fast write speed
• What are the disadvantages of magnetic disks?

  They...

  • lots of mechanical parts
  • durability is an issue
  • sealed unit due to disk head and platter precision
  • not very portable